Currently Kendo MVVM only supports a very simple binding syntax, one view attribute can be bound to one model attribute. I'd like to have real javascript expressions or function calls in bindings to support more complex scenarios, e.g. you only want to show the "submit" button in a form when all fields have been completed.

KnockOutJS supports this: http://knockoutjs.com/documentation/visible-binding.html#note_using_functions_and_expressions_to_control_element_visibility

dataSource: {
       type: "odata",
       typeversion: "3"
}

As of today, it is possible to create custom "simple" bindings as per this code sample:

http://demos.kendoui.com/web/mvvm/custom.html

This works fine, but it would be appreciated to be able to create custom bindings with "complex" syntax, such as this:

data-bind="foo: {condition: somePropertyOnViewModel, option1: A, option2: B }"

Though KendoUI already has an MVVM style binding, it would be much better to have a css binding allowing us to set class on HTML elements based on arbitrary conditions.

Just look at the Knockoutjs css binding.

Something like this:

                        transport: {
                            read: "http://localhost/SentryWebAPI/api/Transactions",
                            datatype: "json",
                            headers: { Authorization: "user/password" }
                        },

NOTE: This syntax actually works now but does not get propagated with the HTTP request Headers.

I think this would be a simple fix as JQuery.$ajax supports this. It would make custom transport level security possible. There are a lot of requests for security and this would allow a roll-your-own method.

Add support for Web Sockets to enable push notifications to grid, listview, and other data bound widgets.

Right aligned columns are common for number fields and it would be nice to simply set a property in HTML and/or the view-model:
E.g { "field": "amount", "align": "right", "title": "Amount", "width": "110" }

Add a visible property to the column items for the grid control. Then provide the value in the view-model. This would allow us to declare the columns in html and manage their visibility in the business logic.

If possible, please consider making the Kendo DataSource compatible with the data returned from using an ASP.NET MVC 4 Web API project possibly by adding a 'webapi' dataType.

Option to refresh one item from a datasource from the server using a GET request using the transport read url appended with the item ID field value.

See: http://www.kendoui.com//forums/framework/data-source/how-to-refresh-an-item-in-a-datasource-with-server-data.aspx

Like many other Kendo components, the treeview is not mature enough to be considered to display dynamic hierarchical data in a LOB application (features limit its use to a static web site).

I can only recommend to urgently add databinding to a datasource. Then you will have to consider loading the dataSource on demand. See http://demos.telerik.com/aspnet-mvc/treeview/ajaxloading

Add support for automatic polling/refresh on DataSource.
Property: interval in milliseconds

It'd be terrific if there was built-in access to client-side data stores (e.g. IndexedDb).

Will you be doing something like KnockoutJS?